This proposal requests funding to acquire an instrumented treadmill (AMTI Corp. Watertown, MA, USA, Model #SBSFIT) for purposes of quantifying ground reaction forces (GRFs). An instrumented treadmill (IT) is essential for gait studies that require subjects to remain stationary with respect to the laboratory or perform more clinically relevant loading scenarios such as inclined walking/running. GRFs coupled with joint kinematics (i.e. joint angles) are essential to obtain joint kinetics (i.e. joint torques/moments). Together, joint kinematics and kinetics provide the foundation of gait analysis, the discipline used to enhance our knowledge of joint biomechanics, provide interventions for patients with gait abnormalities, and/or improve athletic performance. Two facilities on campus can perform motion analysis: 1) the Movement Analysis Lab at Shriners Hospital, and 2) the Motion Capture Core Facility within the Department of Physical Therapy, but both have limited capacity to study a variety of loading scenarios and are not well suited to study motions of subjects with pathological gait. We are in a unique position to couple a recently developed high-speed biplane fluoroscope system with the proposed IT. This system uses markerless registration to align 3D CT models of joints to 2D fluoroscope images, thus replicating in-vivo joint motion with astounding accuracy (~0.1 mm). Integrating the IT with additional existing motion capture technology, including an LED infrared device and an electromagnetic tracking unit, would allow a diverse group of researchers to simultaneously compute 3D joint kinematics and joint kinetics in a single lab. The IT would directly benefit PIs who currently have NIH funding in: Computational Biomechanics, Orthopaedics, Physical Therapy, Bioengineering/Neural Interfaces, and Obstetrics and Gynecology or are pursuing funding in: Exercise and Sport Science, Mechanical Engineering and Ergonomics and Biology. The proposed IT enables a variety of scenarios (i.e. inclined/declined locomotion, precise control of speed) that simply cannot be performed in traditional gait labs. Because ITs reduce the likelihood of a double strike on a single plate and eliminates trials without strikes on any plates, they yield data with less variation and error than those obtained with over-ground force plates, directly translating into fewer trials and less patient fatigue. Unlike gait labs, the proposed IT is mobile and requires working space an order of magnitude less;allowing relocation to facilities where supplemental testing equipment must remain stationary. Therefore, the proposed instrumented treadmill has both a purpose and a substantial need distinct from that of the gait labs currently on campus.